Smoking reduces radiotherapy's effectiveness

Diehard smokers diagnosed with head and neck cancers need to be told that it's never too late to stop smoking, especially if they are about to begin radiation therapy for their smoking-induced disease, according to an article published online this month in Radiotherapy and Oncology.

A Danish study evaluating 232 consecutive patients with squamous cell carcinoma of the larynx, pharynx, and oral cavity who received radiation therapy at Aarhus University Hospital determined that patients who continued to smoke during treatment had worse outcomes than patients who did not (Radiother Oncol, March 3, 2012).

Dr. Camilla Molich Hoff, from the department of experimental clinical oncology, and colleagues suggested that the poorer outcome in locoregional control between smokers (44%) and nonsmokers (65%) during treatment could be attributed to a rise in carboxyhemoglobin level, which reduces the oxygen supply to tumors. Carboxyhemoglobin levels are usually 1% to 2%, whereas smokers can have levels as high as 15% to 20%.

The patients ranged in age from 31 to 87 and were predominantly male (78%). Prior to the start of their treatment, they were asked to complete a questionnaire about lifetime smoking habits. The patients classified themselves as heavy smokers of more than one pack of cigarettes a day (47%), moderate smokers (23%), having quit smoking within 12 months (10%), or having not smoked for at least one year (15%). Five percent of the patients said that they'd never smoked.

The group was followed for at least five years or until they died. The risk of death increased with each additional pack-year of smoking for the group, according to the researchers.

Overall survival rates did not significantly differ between moderate smokers and heavy smokers, but a trend toward a lower survival rate in the heavy smoking group was identified. The difference in overall survival rates at five years was most significant between heavy smokers and nonsmokers, at 39% compared to 66%.